Scotts MossEx controls moss without harming your lawn. After you apply MossEx it will attack undesirable moss, causing it to turn black and disappear. It also contains nutrients to green your lawn and develop thick grass. Apply Scotts MossEx in the winter or spring when moss is actively growing. It is best applied when the lawn is moist and tall grass has been mowed to expose low growing moss. Manufacturer recommends using a Scotts spreader to apply this product. For Scotts rotary/broadcast spreaders, use a setting of 2 for the regular rate or 2 for the heavy rate. For Scotts drop spreaders, use a setting of 4 for the regular rate or 4 for the heavy rate. For Scotts Wizz, use a setting of 3 for the regular rate and 3 for the heavy rate. If additional treatments are needed, wait 2 to 4 weeks between applications. Please note, grass blades may turn black temporarily; however, this condition will disappear after mowing.